Quantum-chromodynamic effects in polarized electroproduction

RUB-TPII-26/95 hep-ph/9509283We investigate the singlet g (0)T and isovector g (3)T tensor charges of the nucleon, which are deeply related to the first moment of the leading twist transversity quark distribution h1(x), in the SU(2) chiral quark-soliton model. With rotational O(1/Nc) corrections taken into account, we obtain g (0) T = 0.69 and g (3) T = 1.45 at a low normalization point of several hundreds MeV. Within the same approximation and parameters the model yields g (0) A = 0.36, g (3) A = 1.21 for axial charges and correct octetdecuplet mass splitting. We show how the chiral quark-soliton model interpolates between the nonrelativistic quark model and the Skyrme model. 11.15. Pg, 13.88.+e, 14.20.Dh The complete information about the quark structure of the nucleon in leading-order hard processes is contained in three twist-two parton distributions. Two of them f 1 (x) and g 1 (x) have been studied extensively theoretically and measured in deep-inelastic scattering experiments [1]. The third transversity quark distribution h 1 (x) is unaccessible for measurements in inclusive deepinelastic experiments. However the h 1 (x) plays an essential role in polarized Drell-Yan processes [2] and other exclusive hard reactions [3,4,5]. The measurement of the h 1 (x) has been proposed recently by the RHIC spin collaboration [6] and HERMES collaboration at HERA [7].The evolution equation for h 1 (x) has been derived in refs. [8,9]. Also it was shown by Jaffe and Ji [5] that the first moment of h 1 (x) is related to the nucleon tensor charge:where f is a flavor index (f = u, d, s, · · ·) and the tensor charge g f T is defined as the forward nucleon matrix element [5,10]:where U (p) is a standard Dirac spinor andIt is convenient to introduce singlet and isovector tensor charges:The tensor charges depend on the renormalization scale and the corresponding anomalous dimension at one loop has been calculated in refs. [2,9]: γ = 2α s /3π. Our aim is to calculate the tensor charges (2) in the chiral quark-soliton model (χQSM, often called the semibosonized Nambu-Jona-Lasinio model) at a low normalization point of several hundreds MeV.The χQSM has been successful in reproducing the static properties of the baryons such as the octet-decuplet mass splitting [11,12,13,14], axial charges [15,16,17,18] and magnetic moments [19,20] and their form factors [19,21] (for details, see the recent review [22]). The baryon in this model is regarded as a bound state of N c quarks bound by a non-trivial chiral field configuration. Such a semiclassical picture of baryons can be justified in the N c → ∞ limit in line with more general arguments by Witten [23]. A remarkable virtue of χQSM is that the model interpolates between the nonrelativistic quark model(NRQM) and the Skyrme model [24]. In particular, due to such an interplay, it enables us to examine the dynamical difference between the axial and tensor charges of the nucleon.In the following, we employ the effective QCD partition function from the instanton picture of QCD in the limit of...

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“…[8,9]. Also it was shown by Jaffe and Ji [5] that the first moment of h 1 (x) is related to the nucleon tensor charge:…”

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Nucleon tensor charges in the SU(2) chiral quark-soliton model

1996

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“…The corresponding anomalous dimension has been evaluated in Refs. [12][13][14]: γ = 2α s /3π. However, their dependence on the normalization point is very weak:…”

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confidence: 99%

Tensor charges of the nucleon in the SU(3) chiral quark soliton model

1996

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The tensor charges of the nucleon are calculated in the framework of the SU(3) chiral quark soliton model. The rotational 1/N c and strange quark mass corrections are taken into account up to linear order. We obtain the following numerical values of the tensor charges: δu = 1.12, δd = −0.42, and δs = −0.008. In contrast to the axial charges, the tensor charges in our model are closer to those of the nonrelativistic quark model, in particular, the net number of the transversely polarized strange quarks in a transversely polarized nucleon δs is compatible with zero.

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“…[10]. For the Bjorken sum rule, the α s correction [11], the α 2 s correction [12], and the α 3 s correction [13] have been calculated in the leading twist approximation. Higher twist corrections have also been calculated [14].…”

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confidence: 99%